A long-running investigation of heroin and weapons trafficking in Rhode Island drew to a close Thursday, with authorities saying it resulted in the arrest of 36 alleged members of the notorious El Salvador-linked MS-13 gang and the seizure of more than 50 pounds of the drug, 15 guns and nearly $500,000 in cash.

U.S. Attorney for Rhode Island Peter Neronha said that in addition to convictions on drug charges, the two-year operation targeting “armed gang activity and associated drug dealing” led to convictions for assault, arson and conspiracy to commit murder -- in connection with a plot against one gang member’s girlfriend.

Fourteen different law enforcement agencies were involved in the investigation dubbed “Operation Gas,” including the FBI, ATF, the U.S. Drug Enforcement Administration, Rhode Island State Police and numerous local agencies, according to a press release issued by the U.S. Attorney’s Office.

“This is an example where another team challenged ours and lost,” said Vincent Lisi, the agent in charge of the FBI’s Providence bureau.

A senior law enforcement source told NBC News that officers seized 12 handguns -- including a Colt .45-caliber revolver, several semi-automatic pistols, and a Ruger Super Blackhawk .45-caliber pistol, a weapon often seen in old Western movies. In addition police recovered three 12-gauge shotguns from the gang.

Among those convicted in connection with the alleged heroin trafficking operation was Jose Fernandez, who is serving more than eight years in prison for drug offenses and an attempt to hire a hitman to kill his girlfriend.

According to the press release, Fernandez shipped heroin concealed in car parts from Guatemala to an auto dealership in Providence where he worked.

The arrest of two other gang members, Jose Dume and Ariel Hassel, resulted in the seizure of almost half a million dollars in cash, jewelry valued at more than $60,000 and a dozen cars in three Rhode Island cities, it said. Dume was identified as the leader of a weapons-trafficking conspiracy and his arrest and led investigators to 14 other alleged gang members.

The drugs seized in the course of the investigation were historic amounts in Rhode Island. Acting on information gathered by Providence Police detectives, two dealers -- Jorge Estrada, 19, and Angel Feliz, 48 -- were arrested by the DEA in October 2012. Police seized three vehicles and 19 kilograms (more than 41 pounds) of heroin valued at $4.5 million -- the largest single seizure ever in the state, according to the relase. Estrada has been sentenced to 15 years in federal prison and Feliz will serve nearly six year.

Several gang members will be in jail for a decade or more only to be deported at the end of their sentence. Another dozen men, identified only by gang nicknames like “Fatty,” “Jumbo” and “Pee-Wee” have already been deported.

The MS-13 Gang has its origins in Los Angeles, born of El Salvadorian immigrants fleeing a civil war in their home country in the mid-1980s. The gang later branched out across the country as Central American immigrants moved to other states.

MS-13 gained national prominence in 2004, after gang members used a machete to chop the hand off the hand of a member of a rival gang in the D.C. suburbs. That incident coupled with other shootings and stabbings in the area led to congressional hearings on the gang’s activities.

Last year the gang whose full name is Mara SalvaTrucha was declared a “transnational criminal organization” by the U.S. Treasury. The declaration gave Treasury the power to freeze financial assets and limits banks from any transactions with the group.